What is the pH of a solution with a [H+] of 1.0 x 10-4 M?

Approximately how many ice cubes must melt to cool 650 milliliters of water from 29°C to 0°C? Assume that each ice cube contains

qwelly [4]

Answer : The number of ice cubes melt must be, 13

Explanation :

First we have to calculate the mass of water.

$\text{Mass of water}=\text{Density of water}\times \text{Volume of water}$

Density of water = 1.00 g/mL

Volume of water = 650 mL

$\text{Mass of water}=1.00g/mL\times 650mL=650g$

Now we have to calculate the heat released on cooling.

Heat released on cooling = $m\times c\times (T_2-T_1)$

where,

m = mass of water = 650 g

c = specific heat capacity of water = $4.18J/g^oC$

$T_2$ = final temperature = $29^oC$

$T_2$ = initial temperature = $0^oC$

Now put all the given values in the above expression, we get:

Heat released on cooling = $650g\times 4.18J/g^oC\times (29-0)^oC$

Heat released on cooling = 78793 J = 78.793 kJ (1 J = 0.001 kJ)

As, 1 ice cube contains 1 mole of water.

The heat required for 1 ice cube to melt = 6.02 kJ

Now we have to calculate the number of ice cubes melted.

Number of ice cubes melted = $\frac{\text{Total heat}}{\text{Heat for 1 ice cube}}$

Number of ice cubes melted = $\frac{78.793kJ}{6.02kJ}$

Number of ice cubes melted = 13.1 ≈ 13

Therefore, the number of ice cubes melt must be, 13

3 0

3 years ago

Metal rings can be coated with a layer of copper using electricity.

Eduardwww [97]

<u>First of all, what is electrolysis?</u>

Electrolysis is the process of breaking down ionic substances using direct current.

<u>Important points about electrolysis </u>

→ Ionic substances contain particles called ions.

→ Electricity is the flow of electrons or ions. For electrolysis to work, the compound must contain ions. The ions must be free to move for electrolysis to occur and it can happen by melting or dissolving an ionic substance in water.

→ Positively charged ions move to the negative electrode. They receive electrons and are <em>reduced</em>. The positive ions move towards the negative electrode because they want to cancel each other out.

→ Negatively charged ions move to the positive electrode. They lose electrons and are <em>oxidised</em>. The substance that is broken down is called the electrolyte <em>(an electrolyte is just a liquid or solution that can conduct electricity)</em> . The negative ions move towards the positive electrode because they want to cancel each other out.

<h3>Cathode = Negative electrode</h3><h3>Anode = Positive electrode</h3>

Metal ions form at the cathode and non-metal ions form at the anode

How I remember if an element is <em>oxidised</em> or <em>reduced</em> is by remembering OIL RIG

OIL = Oxidation is Loss (of electrons)

RIG = Reduction is Gain (of electrons)

<h2><em><u>The answer to your question</u></em></h2>

1) The first step would be to clean the metal ring and sand it down because when the metal atoms from the electrolyte are deposited onto the ring, they will form a weak bond and they may simply 'fall' off. Also this could affect conductivity and the whole experiment. The more things you do accurately now, the more accurate your result will be.

2) You want to put the solution you are given in to the tank your going to be using.

3) This is basically the main part, you want to set up the circuit, I have attached a diagram at the bottom to show you the circuit. The copper rod will be the anode and the metal ring will be a cathode (ignore the elements).

4) Now turn on the circuit and you will start to see the solution spilt with the the solution now being split some going to the anode and some going the cathode.

5) Then a thin layer should form on the electrode.

Hope this helps :)